[RFC,net-next,v5,3/4] virtio_net: Extend virtio to use VF datapath when available

This patch enables virtio_net to switch over to a VF datapath when a VF
netdev is present with the same MAC address. It allows live migration
of a VM with a direct attached VF without the need to setup a bond/team
between a VF and virtio net device in the guest.

The hypervisor needs to enable only one datapath at any time so that
packets don't get looped back to the VM over the other datapath. When a VF
is plugged, the virtio datapath link state can be marked as down. The
hypervisor needs to unplug the VF device from the guest on the source host
and reset the MAC filter of the VF to initiate failover of datapath to
virtio before starting the migration. After the migration is completed,
the destination hypervisor sets the MAC filter on the VF and plugs it back
to the guest to switch over to VF datapath.

When BACKUP feature is enabled, an additional netdev(bypass netdev) is
created that acts as a master device and tracks the state of the 2 lower
netdevs. The original virtio_net netdev is marked as 'backup' netdev and a
passthru device with the same MAC is registered as 'active' netdev.

This patch is based on the discussion initiated by Jesse on this thread.
https://marc.info/?l=linux-virtualization&m=151189725224231&w=2

Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
---
 drivers/net/Kconfig      |   1 +
 drivers/net/virtio_net.c | 612 ++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 612 insertions(+), 1 deletion(-)

Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>This patch enables virtio_net to switch over to a VF datapath when a VF
>netdev is present with the same MAC address. It allows live migration
>of a VM with a direct attached VF without the need to setup a bond/team
>between a VF and virtio net device in the guest.
>
>The hypervisor needs to enable only one datapath at any time so that
>packets don't get looped back to the VM over the other datapath. When a VF
>is plugged, the virtio datapath link state can be marked as down. The
>hypervisor needs to unplug the VF device from the guest on the source host
>and reset the MAC filter of the VF to initiate failover of datapath to
>virtio before starting the migration. After the migration is completed,
>the destination hypervisor sets the MAC filter on the VF and plugs it back
>to the guest to switch over to VF datapath.
>
>When BACKUP feature is enabled, an additional netdev(bypass netdev) is
>created that acts as a master device and tracks the state of the 2 lower
>netdevs. The original virtio_net netdev is marked as 'backup' netdev and a
>passthru device with the same MAC is registered as 'active' netdev.
>
>This patch is based on the discussion initiated by Jesse on this thread.
>https://marc.info/?l=linux-virtualization&m=151189725224231&w=2
>
>Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
>---
> drivers/net/Kconfig      |   1 +
> drivers/net/virtio_net.c | 612 ++++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 612 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
>index 891846655000..9e2cf61fd1c1 100644
>--- a/drivers/net/Kconfig
>+++ b/drivers/net/Kconfig
>@@ -331,6 +331,7 @@ config VETH
> config VIRTIO_NET
> 	tristate "Virtio network driver"
> 	depends on VIRTIO
>+	depends on MAY_USE_BYPASS
> 	---help---
> 	  This is the virtual network driver for virtio.  It can be used with
> 	  QEMU based VMMs (like KVM or Xen).  Say Y or M.
>diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>index befb5944f3fd..86b2f8f2947d 100644
>--- a/drivers/net/virtio_net.c
>+++ b/drivers/net/virtio_net.c
>@@ -30,8 +30,11 @@
> #include <linux/cpu.h>
> #include <linux/average.h>
> #include <linux/filter.h>
>+#include <linux/netdevice.h>
>+#include <linux/pci.h>
> #include <net/route.h>
> #include <net/xdp.h>
>+#include <net/bypass.h>
> 
> static int napi_weight = NAPI_POLL_WEIGHT;
> module_param(napi_weight, int, 0444);
>@@ -206,6 +209,9 @@ struct virtnet_info {
> 	u32 speed;
> 
> 	unsigned long guest_offloads;
>+
>+	/* upper netdev created when BACKUP feature enabled */
>+	struct net_device __rcu *bypass_netdev;
> };
> 
> struct padded_vnet_hdr {
>@@ -2275,6 +2281,22 @@ static int virtnet_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> 	}
> }
> 
>+static int virtnet_get_phys_port_name(struct net_device *dev, char *buf,
>+				      size_t len)
>+{
>+	struct virtnet_info *vi = netdev_priv(dev);
>+	int ret;
>+
>+	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_BACKUP))
>+		return -EOPNOTSUPP;
>+
>+	ret = snprintf(buf, len, "_bkup");
>+	if (ret >= len)
>+		return -EOPNOTSUPP;
>+
>+	return 0;
>+}
>+
> static const struct net_device_ops virtnet_netdev = {
> 	.ndo_open            = virtnet_open,
> 	.ndo_stop   	     = virtnet_close,
>@@ -2292,6 +2314,7 @@ static const struct net_device_ops virtnet_netdev = {
> 	.ndo_xdp_xmit		= virtnet_xdp_xmit,
> 	.ndo_xdp_flush		= virtnet_xdp_flush,
> 	.ndo_features_check	= passthru_features_check,
>+	.ndo_get_phys_port_name	= virtnet_get_phys_port_name,
> };
> 
> static void virtnet_config_changed_work(struct work_struct *work)
>@@ -2689,6 +2712,576 @@ static int virtnet_validate(struct virtio_device *vdev)
> 	return 0;
> }
> 
>+/* START of functions supporting VIRTIO_NET_F_BACKUP feature.
>+ * When BACKUP feature is enabled, an additional netdev(bypass netdev)
>+ * is created that acts as a master device and tracks the state of the
>+ * 2 lower netdevs. The original virtio_net netdev is registered as
>+ * 'backup' netdev and a passthru device with the same MAC is registered
>+ * as 'active' netdev.
>+ */
>+
>+/* bypass state maintained when BACKUP feature is enabled */
>+struct virtnet_bypass_info {
>+	/* passthru netdev with same MAC */
>+	struct net_device __rcu *active_netdev;
>+
>+	/* virtio_net netdev */
>+	struct net_device __rcu *backup_netdev;
>+
>+	/* active netdev stats */
>+	struct rtnl_link_stats64 active_stats;
>+
>+	/* backup netdev stats */
>+	struct rtnl_link_stats64 backup_stats;
>+
>+	/* aggregated stats */
>+	struct rtnl_link_stats64 bypass_stats;
>+
>+	/* spinlock while updating stats */
>+	spinlock_t stats_lock;
>+};
>+
>+static int virtnet_bypass_open(struct net_device *dev)
>+{
>+	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>+	struct net_device *active_netdev, *backup_netdev;
>+	int err;
>+
>+	netif_carrier_off(dev);
>+	netif_tx_wake_all_queues(dev);
>+
>+	active_netdev = rtnl_dereference(vbi->active_netdev);
>+	if (active_netdev) {
>+		err = dev_open(active_netdev);
>+		if (err)
>+			goto err_active_open;
>+	}
>+
>+	backup_netdev = rtnl_dereference(vbi->backup_netdev);
>+	if (backup_netdev) {
>+		err = dev_open(backup_netdev);
>+		if (err)
>+			goto err_backup_open;
>+	}

This should be moved to bypass module.
See "***" below.

>+
>+	return 0;
>+
>+err_backup_open:
>+	dev_close(active_netdev);
>+err_active_open:
>+	netif_tx_disable(dev);
>+	return err;
>+}
>+
>+static int virtnet_bypass_close(struct net_device *dev)
>+{
>+	struct virtnet_bypass_info *vi = netdev_priv(dev);
>+	struct net_device *child_netdev;
>+
>+	netif_tx_disable(dev);
>+
>+	child_netdev = rtnl_dereference(vi->active_netdev);
>+	if (child_netdev)
>+		dev_close(child_netdev);
>+
>+	child_netdev = rtnl_dereference(vi->backup_netdev);
>+	if (child_netdev)
>+		dev_close(child_netdev);

This should be moved to bypass module.

>+
>+	return 0;
>+}
>+
>+static netdev_tx_t virtnet_bypass_drop_xmit(struct sk_buff *skb,
>+					    struct net_device *dev)
>+{
>+	atomic_long_inc(&dev->tx_dropped);
>+	dev_kfree_skb_any(skb);
>+	return NETDEV_TX_OK;
>+}
>+
>+static bool virtnet_bypass_xmit_ready(struct net_device *dev)
>+{
>+	return netif_running(dev) && netif_carrier_ok(dev);
>+}
>+
>+static netdev_tx_t virtnet_bypass_start_xmit(struct sk_buff *skb,
>+					     struct net_device *dev)
>+{
>+	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>+	struct net_device *xmit_dev;
>+
>+	/* Try xmit via active netdev followed by backup netdev */
>+	xmit_dev = rcu_dereference_bh(vbi->active_netdev);
>+	if (!xmit_dev || !virtnet_bypass_xmit_ready(xmit_dev)) {
>+		xmit_dev = rcu_dereference_bh(vbi->backup_netdev);

This should be moved to bypass module.
	
>+		if (!xmit_dev || !virtnet_bypass_xmit_ready(xmit_dev))
>+			return virtnet_bypass_drop_xmit(skb, dev);
>+	}
>+
>+	skb->dev = xmit_dev;
>+	skb->queue_mapping = qdisc_skb_cb(skb)->slave_dev_queue_mapping;
>+
>+	return dev_queue_xmit(skb);
>+}
>+
>+static u16 virtnet_bypass_select_queue(struct net_device *dev,
>+				       struct sk_buff *skb, void *accel_priv,
>+				       select_queue_fallback_t fallback)
>+{
>+	/* This helper function exists to help dev_pick_tx get the correct
>+	 * destination queue.  Using a helper function skips a call to
>+	 * skb_tx_hash and will put the skbs in the queue we expect on their
>+	 * way down to the bonding driver.
>+	 */
>+	u16 txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : 0;
>+
>+	/* Save the original txq to restore before passing to the driver */
>+	qdisc_skb_cb(skb)->slave_dev_queue_mapping = skb->queue_mapping;
>+
>+	if (unlikely(txq >= dev->real_num_tx_queues)) {
>+		do {
>+			txq -= dev->real_num_tx_queues;
>+		} while (txq >= dev->real_num_tx_queues);
>+	}
>+
>+	return txq;
>+}
>+
>+/* fold stats, assuming all rtnl_link_stats64 fields are u64, but
>+ * that some drivers can provide 32bit values only.
>+ */
>+static void virtnet_bypass_fold_stats(struct rtnl_link_stats64 *_res,
>+				      const struct rtnl_link_stats64 *_new,
>+				      const struct rtnl_link_stats64 *_old)
>+{
>+	const u64 *new = (const u64 *)_new;
>+	const u64 *old = (const u64 *)_old;
>+	u64 *res = (u64 *)_res;
>+	int i;
>+
>+	for (i = 0; i < sizeof(*_res) / sizeof(u64); i++) {
>+		u64 nv = new[i];
>+		u64 ov = old[i];
>+		s64 delta = nv - ov;
>+
>+		/* detects if this particular field is 32bit only */
>+		if (((nv | ov) >> 32) == 0)
>+			delta = (s64)(s32)((u32)nv - (u32)ov);
>+
>+		/* filter anomalies, some drivers reset their stats
>+		 * at down/up events.
>+		 */
>+		if (delta > 0)
>+			res[i] += delta;
>+	}
>+}
>+
>+static void virtnet_bypass_get_stats(struct net_device *dev,
>+				     struct rtnl_link_stats64 *stats)
>+{
>+	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>+	const struct rtnl_link_stats64 *new;
>+	struct rtnl_link_stats64 temp;
>+	struct net_device *child_netdev;
>+
>+	spin_lock(&vbi->stats_lock);
>+	memcpy(stats, &vbi->bypass_stats, sizeof(*stats));
>+
>+	rcu_read_lock();
>+
>+	child_netdev = rcu_dereference(vbi->active_netdev);
>+	if (child_netdev) {
>+		new = dev_get_stats(child_netdev, &temp);
>+		virtnet_bypass_fold_stats(stats, new, &vbi->active_stats);
>+		memcpy(&vbi->active_stats, new, sizeof(*new));
>+	}
>+
>+	child_netdev = rcu_dereference(vbi->backup_netdev);
>+	if (child_netdev) {
>+		new = dev_get_stats(child_netdev, &temp);
>+		virtnet_bypass_fold_stats(stats, new, &vbi->backup_stats);
>+		memcpy(&vbi->backup_stats, new, sizeof(*new));
>+	}
>+
>+	rcu_read_unlock();
>+
>+	memcpy(&vbi->bypass_stats, stats, sizeof(*stats));
>+	spin_unlock(&vbi->stats_lock);
>+}

This should be moved to bypass module.

>+
>+static int virtnet_bypass_change_mtu(struct net_device *dev, int new_mtu)
>+{
>+	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>+	struct net_device *active_netdev, *backup_netdev;
>+	int ret = 0;
>+
>+	active_netdev = rcu_dereference(vbi->active_netdev);
>+	if (active_netdev) {
>+		ret = dev_set_mtu(active_netdev, new_mtu);
>+		if (ret)
>+			return ret;
>+	}
>+
>+	backup_netdev = rcu_dereference(vbi->backup_netdev);
>+	if (backup_netdev) {
>+		ret = dev_set_mtu(backup_netdev, new_mtu);
>+		if (ret) {
>+			dev_set_mtu(active_netdev, dev->mtu);
>+			return ret;
>+		}
>+	}
>+
>+	dev->mtu = new_mtu;
>+	return 0;
>+}

This should be moved to bypass module.

	
>+
>+static void virtnet_bypass_set_rx_mode(struct net_device *dev)
>+{
>+	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>+	struct net_device *child_netdev;
>+
>+	rcu_read_lock();
>+
>+	child_netdev = rcu_dereference(vbi->active_netdev);
>+	if (child_netdev) {
>+		dev_uc_sync_multiple(child_netdev, dev);
>+		dev_mc_sync_multiple(child_netdev, dev);
>+	}
>+
>+	child_netdev = rcu_dereference(vbi->backup_netdev);
>+	if (child_netdev) {
>+		dev_uc_sync_multiple(child_netdev, dev);
>+		dev_mc_sync_multiple(child_netdev, dev);
>+	}
>+
>+	rcu_read_unlock();
>+}

This should be moved to bypass module.


>+
>+static const struct net_device_ops virtnet_bypass_netdev_ops = {
>+	.ndo_open		= virtnet_bypass_open,
>+	.ndo_stop		= virtnet_bypass_close,
>+	.ndo_start_xmit		= virtnet_bypass_start_xmit,
>+	.ndo_select_queue	= virtnet_bypass_select_queue,
>+	.ndo_get_stats64	= virtnet_bypass_get_stats,
>+	.ndo_change_mtu		= virtnet_bypass_change_mtu,
>+	.ndo_set_rx_mode	= virtnet_bypass_set_rx_mode,
>+	.ndo_validate_addr	= eth_validate_addr,
>+	.ndo_features_check	= passthru_features_check,
>+};
>+
>+static int
>+virtnet_bypass_ethtool_get_link_ksettings(struct net_device *dev,
>+					  struct ethtool_link_ksettings *cmd)
>+{
>+	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>+	struct net_device *child_netdev;
>+
>+	child_netdev = rtnl_dereference(vbi->active_netdev);
>+	if (!child_netdev || !virtnet_bypass_xmit_ready(child_netdev)) {
>+		child_netdev = rtnl_dereference(vbi->backup_netdev);
>+		if (!child_netdev || !virtnet_bypass_xmit_ready(child_netdev)) {
>+			cmd->base.duplex = DUPLEX_UNKNOWN;
>+			cmd->base.port = PORT_OTHER;
>+			cmd->base.speed = SPEED_UNKNOWN;
>+
>+			return 0;
>+		}
>+	}
>+
>+	return __ethtool_get_link_ksettings(child_netdev, cmd);
>+}
>+
>+#define BYPASS_DRV_NAME "virtnet_bypass"
>+#define BYPASS_DRV_VERSION "0.1"
>+
>+static void virtnet_bypass_ethtool_get_drvinfo(struct net_device *dev,
>+					       struct ethtool_drvinfo *drvinfo)
>+{
>+	strlcpy(drvinfo->driver, BYPASS_DRV_NAME, sizeof(drvinfo->driver));
>+	strlcpy(drvinfo->version, BYPASS_DRV_VERSION, sizeof(drvinfo->version));
>+}
>+
>+static const struct ethtool_ops virtnet_bypass_ethtool_ops = {
>+	.get_drvinfo            = virtnet_bypass_ethtool_get_drvinfo,
>+	.get_link               = ethtool_op_get_link,
>+	.get_link_ksettings     = virtnet_bypass_ethtool_get_link_ksettings,
>+};
>+
>+static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>+				     struct net_device *child_netdev)
>+{
>+	struct virtnet_bypass_info *vbi;
>+	bool backup;
>+
>+	vbi = netdev_priv(bypass_netdev);
>+	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>+	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>+			rtnl_dereference(vbi->active_netdev)) {
>+		netdev_info(bypass_netdev,
>+			    "%s attempting to join bypass dev when %s already present\n",
>+			    child_netdev->name, backup ? "backup" : "active");

Bypass module should check if there is already some other netdev
enslaved and refuse right there.

The active/backup terminology is quite confusing. From the bonding world
that means active is the one which is currently used for tx of the
packets. And it depends on link and other things what netdev is declared
active. However here, it is different. Backup is always the virtio_net
instance even when it is active. Odd. Please change the terminology.
For "active" I suggest to use name "stolen".

*** Also, the 2 slave netdev pointers should be stored in the bypass
module instance, not in the drivers.



>+		return -EEXIST;
>+	}
>+
>+	dev_hold(child_netdev);
>+
>+	if (backup) {
>+		rcu_assign_pointer(vbi->backup_netdev, child_netdev);
>+		dev_get_stats(vbi->backup_netdev, &vbi->backup_stats);
>+	} else {
>+		rcu_assign_pointer(vbi->active_netdev, child_netdev);
>+		dev_get_stats(vbi->active_netdev, &vbi->active_stats);
>+		bypass_netdev->min_mtu = child_netdev->min_mtu;
>+		bypass_netdev->max_mtu = child_netdev->max_mtu;
>+	}
>+
>+	netdev_info(bypass_netdev, "child:%s joined\n", child_netdev->name);
>+
>+	return 0;
>+}
>+
>+static int virtnet_bypass_register_child(struct net_device *bypass_netdev,
>+					 struct net_device *child_netdev)
>+{
>+	struct virtnet_bypass_info *vbi;
>+	bool backup;
>+
>+	vbi = netdev_priv(bypass_netdev);
>+	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>+	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>+			rtnl_dereference(vbi->active_netdev)) {
>+		netdev_info(bypass_netdev,
>+			    "%s attempting to register bypass dev when %s already present\n",
>+			    child_netdev->name, backup ? "backup" : "active");
>+		return -EEXIST;
>+	}
>+
>+	/* Avoid non pci devices as active netdev */
>+	if (!backup && (!child_netdev->dev.parent ||
>+			!dev_is_pci(child_netdev->dev.parent)))
>+		return -EINVAL;
>+
>+	netdev_info(bypass_netdev, "child:%s registered\n", child_netdev->name);
>+
>+	return 0;
>+}
>+
>+static int virtnet_bypass_release_child(struct net_device *bypass_netdev,
>+					struct net_device *child_netdev)
>+{
>+	struct net_device *backup_netdev, *active_netdev;
>+	struct virtnet_bypass_info *vbi;
>+
>+	vbi = netdev_priv(bypass_netdev);
>+	active_netdev = rtnl_dereference(vbi->active_netdev);
>+	backup_netdev = rtnl_dereference(vbi->backup_netdev);
>+
>+	if (child_netdev != active_netdev && child_netdev != backup_netdev)
>+		return -EINVAL;
>+
>+	netdev_info(bypass_netdev, "child:%s released\n", child_netdev->name);
>+
>+	return 0;
>+}
>+
>+static int virtnet_bypass_unregister_child(struct net_device *bypass_netdev,
>+					   struct net_device *child_netdev)
>+{
>+	struct net_device *backup_netdev, *active_netdev;
>+	struct virtnet_bypass_info *vbi;
>+
>+	vbi = netdev_priv(bypass_netdev);
>+	active_netdev = rtnl_dereference(vbi->active_netdev);
>+	backup_netdev = rtnl_dereference(vbi->backup_netdev);
>+
>+	if (child_netdev != active_netdev && child_netdev != backup_netdev)
>+		return -EINVAL;
>+
>+	if (child_netdev == backup_netdev) {
>+		RCU_INIT_POINTER(vbi->backup_netdev, NULL);
>+	} else {
>+		RCU_INIT_POINTER(vbi->active_netdev, NULL);
>+		if (backup_netdev) {
>+			bypass_netdev->min_mtu = backup_netdev->min_mtu;
>+			bypass_netdev->max_mtu = backup_netdev->max_mtu;
>+		}
>+	}
>+
>+	dev_put(child_netdev);
>+
>+	netdev_info(bypass_netdev, "child:%s unregistered\n",
>+		    child_netdev->name);
>+
>+	return 0;
>+}
>+
>+static int virtnet_bypass_update_link(struct net_device *bypass_netdev,
>+				      struct net_device *child_netdev)
>+{
>+	struct net_device *active_netdev, *backup_netdev;
>+	struct virtnet_bypass_info *vbi;
>+
>+	if (!netif_running(bypass_netdev))
>+		return 0;
>+
>+	vbi = netdev_priv(bypass_netdev);
>+
>+	active_netdev = rtnl_dereference(vbi->active_netdev);
>+	backup_netdev = rtnl_dereference(vbi->backup_netdev);
>+
>+	if (child_netdev != active_netdev && child_netdev != backup_netdev)
>+		return -EINVAL;
>+
>+	if ((active_netdev && virtnet_bypass_xmit_ready(active_netdev)) ||
>+	    (backup_netdev && virtnet_bypass_xmit_ready(backup_netdev))) {
>+		netif_carrier_on(bypass_netdev);
>+		netif_tx_wake_all_queues(bypass_netdev);
>+	} else {
>+		netif_carrier_off(bypass_netdev);
>+		netif_tx_stop_all_queues(bypass_netdev);
>+	}
>+
>+	return 0;
>+}
>+
>+/* Called when child dev is injecting data into network stack.
>+ * Change the associated network device from lower dev to virtio.
>+ * note: already called with rcu_read_lock
>+ */
>+static rx_handler_result_t virtnet_bypass_handle_frame(struct sk_buff **pskb)
>+{
>+	struct sk_buff *skb = *pskb;
>+	struct net_device *ndev = rcu_dereference(skb->dev->rx_handler_data);
>+
>+	skb->dev = ndev;
>+
>+	return RX_HANDLER_ANOTHER;
>+}

Hmm, you have the rx_handler defined in drivers and you register it in
bypass module. It is odd because here you assume that the bypass module
passed "ndev" and rx_handler_data. Also, you don't need advanced
features rx_handler provides.
Instead, just register a common rx_handler defined in the bypass module
and have simple skb_rx callback here (static void).


>+
>+static const struct bypass_ops virtnet_bypass_ops = {
>+	.register_child		= virtnet_bypass_register_child,
>+	.join_child		= virtnet_bypass_join_child,
>+	.unregister_child	= virtnet_bypass_unregister_child,
>+	.release_child		= virtnet_bypass_release_child,
>+	.update_link		= virtnet_bypass_update_link,
>+	.handle_frame		= virtnet_bypass_handle_frame,
>+};
>+
>+static struct bypass *virtnet_bypass;
>+
>+static int virtnet_bypass_create(struct virtnet_info *vi)
>+{
>+	struct net_device *backup_netdev = vi->dev;
>+	struct device *dev = &vi->vdev->dev;
>+	struct net_device *bypass_netdev;
>+	int res;
>+
>+	/* Alloc at least 2 queues, for now we are going with 16 assuming
>+	 * that most devices being bonded won't have too many queues.
>+	 */
>+	bypass_netdev = alloc_etherdev_mq(sizeof(struct virtnet_bypass_info),
>+					  16);
>+	if (!bypass_netdev) {
>+		dev_err(dev, "Unable to allocate bypass_netdev!\n");
>+		return -ENOMEM;
>+	}
>+
>+	dev_net_set(bypass_netdev, dev_net(backup_netdev));
>+	SET_NETDEV_DEV(bypass_netdev, dev);
>+
>+	bypass_netdev->netdev_ops = &virtnet_bypass_netdev_ops;
>+	bypass_netdev->ethtool_ops = &virtnet_bypass_ethtool_ops;
>+
>+	/* Initialize the device options */
>+	bypass_netdev->flags |= IFF_MASTER;

I think I pointed that out already. Don't use "IFF_MASTER". That is
specific to bonding. As I suggested in the reply to the patch #2, you
should introduce IFF_BYPASS. Also, this flag should be set by the bypass
module. Just create the netdev and do things specific to virtio and then
call to bypass module, pass the netdev so it can do the rest. I think
that the flags, features etc would be also fine to set there.


>+	bypass_netdev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
>+	bypass_netdev->priv_flags &= ~(IFF_XMIT_DST_RELEASE |
>+				       IFF_TX_SKB_SHARING);
>+
>+	/* don't acquire bypass netdev's netif_tx_lock when transmitting */
>+	bypass_netdev->features |= NETIF_F_LLTX;
>+
>+	/* Don't allow bypass devices to change network namespaces. */
>+	bypass_netdev->features |= NETIF_F_NETNS_LOCAL;
>+
>+	bypass_netdev->hw_features = NETIF_F_HW_CSUM | NETIF_F_SG |
>+				     NETIF_F_FRAGLIST | NETIF_F_ALL_TSO |
>+				     NETIF_F_HIGHDMA | NETIF_F_LRO;
>+
>+	bypass_netdev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
>+	bypass_netdev->features |= bypass_netdev->hw_features;
>+
>+	/* For now treat bypass netdev as VLAN challenged since we
>+	 * cannot assume VLAN functionality with a VF

Why? I don't see such drivers. But to be 100% correct, you should check
the NETIF_F_VLAN_CHALLENGED feature in bypass module during VF enslave
and forbid to do so if it is on.


>+	 */
>+	bypass_netdev->features |= NETIF_F_VLAN_CHALLENGED;
>+
>+	memcpy(bypass_netdev->dev_addr, backup_netdev->dev_addr,
>+	       bypass_netdev->addr_len);
>+
>+	bypass_netdev->min_mtu = backup_netdev->min_mtu;
>+	bypass_netdev->max_mtu = backup_netdev->max_mtu;
>+
>+	res = register_netdev(bypass_netdev);
>+	if (res < 0) {
>+		dev_err(dev, "Unable to register bypass_netdev!\n");
>+		goto err_register_netdev;
>+	}
>+
>+	netif_carrier_off(bypass_netdev);
>+
>+	res = bypass_register_instance(virtnet_bypass, bypass_netdev);
>+	if (res < 0)
>+		goto err_bypass;
>+
>+	rcu_assign_pointer(vi->bypass_netdev, bypass_netdev);
>+
>+	return 0;
>+
>+err_bypass:
>+	unregister_netdev(bypass_netdev);
>+err_register_netdev:
>+	free_netdev(bypass_netdev);
>+
>+	return res;
>+}
>+
>+static void virtnet_bypass_destroy(struct virtnet_info *vi)
>+{
>+	struct net_device *bypass_netdev;
>+	struct virtnet_bypass_info *vbi;
>+	struct net_device *child_netdev;
>+
>+	bypass_netdev = rcu_dereference(vi->bypass_netdev);
>+	/* no device found, nothing to free */
>+	if (!bypass_netdev)
>+		return;
>+
>+	vbi = netdev_priv(bypass_netdev);
>+
>+	netif_device_detach(bypass_netdev);
>+
>+	rtnl_lock();
>+
>+	child_netdev = rtnl_dereference(vbi->active_netdev);
>+	if (child_netdev)
>+		bypass_unregister_child(child_netdev);
>+
>+	child_netdev = rtnl_dereference(vbi->backup_netdev);
>+	if (child_netdev)
>+		bypass_unregister_child(child_netdev);
>+
>+	unregister_netdevice(bypass_netdev);
>+
>+	bypass_unregister_instance(virtnet_bypass, bypass_netdev);
>+
>+	rtnl_unlock();
>+
>+	free_netdev(bypass_netdev);
>+}
>+
>+/* END of functions supporting VIRTIO_NET_F_BACKUP feature. */
>+
> static int virtnet_probe(struct virtio_device *vdev)
> {
> 	int i, err = -ENOMEM;
>@@ -2839,10 +3432,15 @@ static int virtnet_probe(struct virtio_device *vdev)
> 
> 	virtnet_init_settings(dev);
> 
>+	if (virtio_has_feature(vdev, VIRTIO_NET_F_BACKUP)) {
>+		if (virtnet_bypass_create(vi) != 0)

You need to do:
		err = virtnet_bypass_create(vi);
		if (err)
otherwise you ignore err and virtnet_probe would return 0;


>+			goto free_vqs;
>+	}
>+
> 	err = register_netdev(dev);
> 	if (err) {
> 		pr_debug("virtio_net: registering device failed\n");
>-		goto free_vqs;
>+		goto free_bypass;
> 	}
> 
> 	virtio_device_ready(vdev);
>@@ -2879,6 +3477,8 @@ static int virtnet_probe(struct virtio_device *vdev)
> 	vi->vdev->config->reset(vdev);
> 
> 	unregister_netdev(dev);
>+free_bypass:
>+	virtnet_bypass_destroy(vi);
> free_vqs:
> 	cancel_delayed_work_sync(&vi->refill);
> 	free_receive_page_frags(vi);
>@@ -2913,6 +3513,8 @@ static void virtnet_remove(struct virtio_device *vdev)
> 
> 	unregister_netdev(vi->dev);
> 
>+	virtnet_bypass_destroy(vi);
>+
> 	remove_vq_common(vi);
> 
> 	free_netdev(vi->dev);
>@@ -2996,6 +3598,11 @@ static __init int virtio_net_driver_init(void)
> {
> 	int ret;
> 
>+	virtnet_bypass = bypass_register_driver(&virtnet_bypass_ops,
>+						&virtnet_bypass_netdev_ops);
>+	if (!virtnet_bypass)
>+		return -ENOMEM;

If CONFIG_NET_BYPASS is undefined, you will always return -ENOMEM here.


>+
> 	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "virtio/net:online",
> 				      virtnet_cpu_online,
> 				      virtnet_cpu_down_prep);
>@@ -3010,12 +3617,14 @@ static __init int virtio_net_driver_init(void)
>         ret = register_virtio_driver(&virtio_net_driver);
> 	if (ret)
> 		goto err_virtio;
>+
> 	return 0;
> err_virtio:
> 	cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
> err_dead:
> 	cpuhp_remove_multi_state(virtionet_online);
> out:
>+	bypass_unregister_driver(virtnet_bypass);
> 	return ret;
> }
> module_init(virtio_net_driver_init);
>@@ -3025,6 +3634,7 @@ static __exit void virtio_net_driver_exit(void)
> 	unregister_virtio_driver(&virtio_net_driver);
> 	cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
> 	cpuhp_remove_multi_state(virtionet_online);
>+	bypass_unregister_driver(virtnet_bypass);
> }
> module_exit(virtio_net_driver_exit);
> 
>-- 
>2.14.3
>

On 4/6/2018 5:48 AM, Jiri Pirko wrote:
> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:

<snip>
> 	
>> +
>> +static void virtnet_bypass_set_rx_mode(struct net_device *dev)
>> +{
>> +	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>> +	struct net_device *child_netdev;
>> +
>> +	rcu_read_lock();
>> +
>> +	child_netdev = rcu_dereference(vbi->active_netdev);
>> +	if (child_netdev) {
>> +		dev_uc_sync_multiple(child_netdev, dev);
>> +		dev_mc_sync_multiple(child_netdev, dev);
>> +	}
>> +
>> +	child_netdev = rcu_dereference(vbi->backup_netdev);
>> +	if (child_netdev) {
>> +		dev_uc_sync_multiple(child_netdev, dev);
>> +		dev_mc_sync_multiple(child_netdev, dev);
>> +	}
>> +
>> +	rcu_read_unlock();
>> +}
> This should be moved to bypass module.

Sure. All these bypass ndo_ops can be moved to bypass module and any
paravirtual driver that want to go with 3 netdev model can reuse these functions.


>
>
>> +
>> +static const struct net_device_ops virtnet_bypass_netdev_ops = {
>> +	.ndo_open		= virtnet_bypass_open,
>> +	.ndo_stop		= virtnet_bypass_close,
>> +	.ndo_start_xmit		= virtnet_bypass_start_xmit,
>> +	.ndo_select_queue	= virtnet_bypass_select_queue,
>> +	.ndo_get_stats64	= virtnet_bypass_get_stats,
>> +	.ndo_change_mtu		= virtnet_bypass_change_mtu,
>> +	.ndo_set_rx_mode	= virtnet_bypass_set_rx_mode,
>> +	.ndo_validate_addr	= eth_validate_addr,
>> +	.ndo_features_check	= passthru_features_check,
>> +};
>> +
>> +static int
>> +virtnet_bypass_ethtool_get_link_ksettings(struct net_device *dev,
>> +					  struct ethtool_link_ksettings *cmd)
>> +{
>> +	struct virtnet_bypass_info *vbi = netdev_priv(dev);
>> +	struct net_device *child_netdev;
>> +
>> +	child_netdev = rtnl_dereference(vbi->active_netdev);
>> +	if (!child_netdev || !virtnet_bypass_xmit_ready(child_netdev)) {
>> +		child_netdev = rtnl_dereference(vbi->backup_netdev);
>> +		if (!child_netdev || !virtnet_bypass_xmit_ready(child_netdev)) {
>> +			cmd->base.duplex = DUPLEX_UNKNOWN;
>> +			cmd->base.port = PORT_OTHER;
>> +			cmd->base.speed = SPEED_UNKNOWN;
>> +
>> +			return 0;
>> +		}
>> +	}
>> +
>> +	return __ethtool_get_link_ksettings(child_netdev, cmd);
>> +}
>> +
>> +#define BYPASS_DRV_NAME "virtnet_bypass"
>> +#define BYPASS_DRV_VERSION "0.1"
>> +
>> +static void virtnet_bypass_ethtool_get_drvinfo(struct net_device *dev,
>> +					       struct ethtool_drvinfo *drvinfo)
>> +{
>> +	strlcpy(drvinfo->driver, BYPASS_DRV_NAME, sizeof(drvinfo->driver));
>> +	strlcpy(drvinfo->version, BYPASS_DRV_VERSION, sizeof(drvinfo->version));
>> +}
>> +
>> +static const struct ethtool_ops virtnet_bypass_ethtool_ops = {
>> +	.get_drvinfo            = virtnet_bypass_ethtool_get_drvinfo,
>> +	.get_link               = ethtool_op_get_link,
>> +	.get_link_ksettings     = virtnet_bypass_ethtool_get_link_ksettings,
>> +};
>> +
>> +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> +				     struct net_device *child_netdev)
>> +{
>> +	struct virtnet_bypass_info *vbi;
>> +	bool backup;
>> +
>> +	vbi = netdev_priv(bypass_netdev);
>> +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> +			rtnl_dereference(vbi->active_netdev)) {
>> +		netdev_info(bypass_netdev,
>> +			    "%s attempting to join bypass dev when %s already present\n",
>> +			    child_netdev->name, backup ? "backup" : "active");
> Bypass module should check if there is already some other netdev
> enslaved and refuse right there.

This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
as its bypass_netdev is same as the backup_netdev.
Will add a flag while registering with the bypass module to indicate if the driver is doing
a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
for 3 netdev scenario.



>
> The active/backup terminology is quite confusing. From the bonding world
> that means active is the one which is currently used for tx of the
> packets. And it depends on link and other things what netdev is declared
> active. However here, it is different. Backup is always the virtio_net
> instance even when it is active. Odd. Please change the terminology.
> For "active" I suggest to use name "stolen".

I am not too happy with 'stolen' name. Will see if i can come up with a
better name.


>
> *** Also, the 2 slave netdev pointers should be stored in the bypass
> module instance, not in the drivers.

Will move virtnet_bypass_info struct to bypass.h

>
>
>
>> +		return -EEXIST;
>> +	}
>> +
>> +	dev_hold(child_netdev);
>> +
>> +	if (backup) {
>> +		rcu_assign_pointer(vbi->backup_netdev, child_netdev);
>> +		dev_get_stats(vbi->backup_netdev, &vbi->backup_stats);
>> +	} else {
>> +		rcu_assign_pointer(vbi->active_netdev, child_netdev);
>> +		dev_get_stats(vbi->active_netdev, &vbi->active_stats);
>> +		bypass_netdev->min_mtu = child_netdev->min_mtu;
>> +		bypass_netdev->max_mtu = child_netdev->max_mtu;
>> +	}
>> +
>> +	netdev_info(bypass_netdev, "child:%s joined\n", child_netdev->name);
>> +
>> +	return 0;
>> +}
>> +
>> +static int virtnet_bypass_register_child(struct net_device *bypass_netdev,
>> +					 struct net_device *child_netdev)
>> +{
>> +	struct virtnet_bypass_info *vbi;
>> +	bool backup;
>> +
>> +	vbi = netdev_priv(bypass_netdev);
>> +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> +			rtnl_dereference(vbi->active_netdev)) {
>> +		netdev_info(bypass_netdev,
>> +			    "%s attempting to register bypass dev when %s already present\n",
>> +			    child_netdev->name, backup ? "backup" : "active");
>> +		return -EEXIST;
>> +	}
>> +
>> +	/* Avoid non pci devices as active netdev */
>> +	if (!backup && (!child_netdev->dev.parent ||
>> +			!dev_is_pci(child_netdev->dev.parent)))
>> +		return -EINVAL;
>> +
>> +	netdev_info(bypass_netdev, "child:%s registered\n", child_netdev->name);
>> +
>> +	return 0;
>> +}
>> +
>> +static int virtnet_bypass_release_child(struct net_device *bypass_netdev,
>> +					struct net_device *child_netdev)
>> +{
>> +	struct net_device *backup_netdev, *active_netdev;
>> +	struct virtnet_bypass_info *vbi;
>> +
>> +	vbi = netdev_priv(bypass_netdev);
>> +	active_netdev = rtnl_dereference(vbi->active_netdev);
>> +	backup_netdev = rtnl_dereference(vbi->backup_netdev);
>> +
>> +	if (child_netdev != active_netdev && child_netdev != backup_netdev)
>> +		return -EINVAL;
>> +
>> +	netdev_info(bypass_netdev, "child:%s released\n", child_netdev->name);
>> +
>> +	return 0;
>> +}
>> +
>> +static int virtnet_bypass_unregister_child(struct net_device *bypass_netdev,
>> +					   struct net_device *child_netdev)
>> +{
>> +	struct net_device *backup_netdev, *active_netdev;
>> +	struct virtnet_bypass_info *vbi;
>> +
>> +	vbi = netdev_priv(bypass_netdev);
>> +	active_netdev = rtnl_dereference(vbi->active_netdev);
>> +	backup_netdev = rtnl_dereference(vbi->backup_netdev);
>> +
>> +	if (child_netdev != active_netdev && child_netdev != backup_netdev)
>> +		return -EINVAL;
>> +
>> +	if (child_netdev == backup_netdev) {
>> +		RCU_INIT_POINTER(vbi->backup_netdev, NULL);
>> +	} else {
>> +		RCU_INIT_POINTER(vbi->active_netdev, NULL);
>> +		if (backup_netdev) {
>> +			bypass_netdev->min_mtu = backup_netdev->min_mtu;
>> +			bypass_netdev->max_mtu = backup_netdev->max_mtu;
>> +		}
>> +	}
>> +
>> +	dev_put(child_netdev);
>> +
>> +	netdev_info(bypass_netdev, "child:%s unregistered\n",
>> +		    child_netdev->name);
>> +
>> +	return 0;
>> +}
>> +
>> +static int virtnet_bypass_update_link(struct net_device *bypass_netdev,
>> +				      struct net_device *child_netdev)
>> +{
>> +	struct net_device *active_netdev, *backup_netdev;
>> +	struct virtnet_bypass_info *vbi;
>> +
>> +	if (!netif_running(bypass_netdev))
>> +		return 0;
>> +
>> +	vbi = netdev_priv(bypass_netdev);
>> +
>> +	active_netdev = rtnl_dereference(vbi->active_netdev);
>> +	backup_netdev = rtnl_dereference(vbi->backup_netdev);
>> +
>> +	if (child_netdev != active_netdev && child_netdev != backup_netdev)
>> +		return -EINVAL;
>> +
>> +	if ((active_netdev && virtnet_bypass_xmit_ready(active_netdev)) ||
>> +	    (backup_netdev && virtnet_bypass_xmit_ready(backup_netdev))) {
>> +		netif_carrier_on(bypass_netdev);
>> +		netif_tx_wake_all_queues(bypass_netdev);
>> +	} else {
>> +		netif_carrier_off(bypass_netdev);
>> +		netif_tx_stop_all_queues(bypass_netdev);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +/* Called when child dev is injecting data into network stack.
>> + * Change the associated network device from lower dev to virtio.
>> + * note: already called with rcu_read_lock
>> + */
>> +static rx_handler_result_t virtnet_bypass_handle_frame(struct sk_buff **pskb)
>> +{
>> +	struct sk_buff *skb = *pskb;
>> +	struct net_device *ndev = rcu_dereference(skb->dev->rx_handler_data);
>> +
>> +	skb->dev = ndev;
>> +
>> +	return RX_HANDLER_ANOTHER;
>> +}
> Hmm, you have the rx_handler defined in drivers and you register it in
> bypass module. It is odd because here you assume that the bypass module
> passed "ndev" and rx_handler_data. Also, you don't need advanced
> features rx_handler provides.
> Instead, just register a common rx_handler defined in the bypass module
> and have simple skb_rx callback here (static void).

Will move the rx_handler also to bypass.c


>
>
>> +
>> +static const struct bypass_ops virtnet_bypass_ops = {
>> +	.register_child		= virtnet_bypass_register_child,
>> +	.join_child		= virtnet_bypass_join_child,
>> +	.unregister_child	= virtnet_bypass_unregister_child,
>> +	.release_child		= virtnet_bypass_release_child,
>> +	.update_link		= virtnet_bypass_update_link,
>> +	.handle_frame		= virtnet_bypass_handle_frame,
>> +};
>> +
>> +static struct bypass *virtnet_bypass;
>> +
>> +static int virtnet_bypass_create(struct virtnet_info *vi)
>> +{
>> +	struct net_device *backup_netdev = vi->dev;
>> +	struct device *dev = &vi->vdev->dev;
>> +	struct net_device *bypass_netdev;
>> +	int res;
>> +
>> +	/* Alloc at least 2 queues, for now we are going with 16 assuming
>> +	 * that most devices being bonded won't have too many queues.
>> +	 */
>> +	bypass_netdev = alloc_etherdev_mq(sizeof(struct virtnet_bypass_info),
>> +					  16);
>> +	if (!bypass_netdev) {
>> +		dev_err(dev, "Unable to allocate bypass_netdev!\n");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	dev_net_set(bypass_netdev, dev_net(backup_netdev));
>> +	SET_NETDEV_DEV(bypass_netdev, dev);
>> +
>> +	bypass_netdev->netdev_ops = &virtnet_bypass_netdev_ops;
>> +	bypass_netdev->ethtool_ops = &virtnet_bypass_ethtool_ops;
>> +
>> +	/* Initialize the device options */
>> +	bypass_netdev->flags |= IFF_MASTER;
> I think I pointed that out already. Don't use "IFF_MASTER". That is
> specific to bonding. As I suggested in the reply to the patch #2, you
> should introduce IFF_BYPASS. Also, this flag should be set by the bypass
> module. Just create the netdev and do things specific to virtio and then
> call to bypass module, pass the netdev so it can do the rest. I think
> that the flags, features etc would be also fine to set there.

OK.


>
>
>> +	bypass_netdev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
>> +	bypass_netdev->priv_flags &= ~(IFF_XMIT_DST_RELEASE |
>> +				       IFF_TX_SKB_SHARING);
>> +
>> +	/* don't acquire bypass netdev's netif_tx_lock when transmitting */
>> +	bypass_netdev->features |= NETIF_F_LLTX;
>> +
>> +	/* Don't allow bypass devices to change network namespaces. */
>> +	bypass_netdev->features |= NETIF_F_NETNS_LOCAL;
>> +
>> +	bypass_netdev->hw_features = NETIF_F_HW_CSUM | NETIF_F_SG |
>> +				     NETIF_F_FRAGLIST | NETIF_F_ALL_TSO |
>> +				     NETIF_F_HIGHDMA | NETIF_F_LRO;
>> +
>> +	bypass_netdev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
>> +	bypass_netdev->features |= bypass_netdev->hw_features;
>> +
>> +	/* For now treat bypass netdev as VLAN challenged since we
>> +	 * cannot assume VLAN functionality with a VF
> Why? I don't see such drivers. But to be 100% correct, you should check
> the NETIF_F_VLAN_CHALLENGED feature in bypass module during VF enslave
> and forbid to do so if it is on.

Will look into it.


>
>
>> +	 */
>> +	bypass_netdev->features |= NETIF_F_VLAN_CHALLENGED;
>> +
>> +	memcpy(bypass_netdev->dev_addr, backup_netdev->dev_addr,
>> +	       bypass_netdev->addr_len);
>> +
>> +	bypass_netdev->min_mtu = backup_netdev->min_mtu;
>> +	bypass_netdev->max_mtu = backup_netdev->max_mtu;
>> +
>> +	res = register_netdev(bypass_netdev);
>> +	if (res < 0) {
>> +		dev_err(dev, "Unable to register bypass_netdev!\n");
>> +		goto err_register_netdev;
>> +	}
>> +
>> +	netif_carrier_off(bypass_netdev);
>> +
>> +	res = bypass_register_instance(virtnet_bypass, bypass_netdev);
>> +	if (res < 0)
>> +		goto err_bypass;
>> +
>> +	rcu_assign_pointer(vi->bypass_netdev, bypass_netdev);
>> +
>> +	return 0;
>> +
>> +err_bypass:
>> +	unregister_netdev(bypass_netdev);
>> +err_register_netdev:
>> +	free_netdev(bypass_netdev);
>> +
>> +	return res;
>> +}
>> +
>> +static void virtnet_bypass_destroy(struct virtnet_info *vi)
>> +{
>> +	struct net_device *bypass_netdev;
>> +	struct virtnet_bypass_info *vbi;
>> +	struct net_device *child_netdev;
>> +
>> +	bypass_netdev = rcu_dereference(vi->bypass_netdev);
>> +	/* no device found, nothing to free */
>> +	if (!bypass_netdev)
>> +		return;
>> +
>> +	vbi = netdev_priv(bypass_netdev);
>> +
>> +	netif_device_detach(bypass_netdev);
>> +
>> +	rtnl_lock();
>> +
>> +	child_netdev = rtnl_dereference(vbi->active_netdev);
>> +	if (child_netdev)
>> +		bypass_unregister_child(child_netdev);
>> +
>> +	child_netdev = rtnl_dereference(vbi->backup_netdev);
>> +	if (child_netdev)
>> +		bypass_unregister_child(child_netdev);
>> +
>> +	unregister_netdevice(bypass_netdev);
>> +
>> +	bypass_unregister_instance(virtnet_bypass, bypass_netdev);
>> +
>> +	rtnl_unlock();
>> +
>> +	free_netdev(bypass_netdev);
>> +}
>> +
>> +/* END of functions supporting VIRTIO_NET_F_BACKUP feature. */
>> +
>> static int virtnet_probe(struct virtio_device *vdev)
>> {
>> 	int i, err = -ENOMEM;
>> @@ -2839,10 +3432,15 @@ static int virtnet_probe(struct virtio_device *vdev)
>>
>> 	virtnet_init_settings(dev);
>>
>> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_BACKUP)) {
>> +		if (virtnet_bypass_create(vi) != 0)
> You need to do:
> 		err = virtnet_bypass_create(vi);
> 		if (err)
> otherwise you ignore err and virtnet_probe would return 0;

Sure.


>
>
>> +			goto free_vqs;
>> +	}
>> +
>> 	err = register_netdev(dev);
>> 	if (err) {
>> 		pr_debug("virtio_net: registering device failed\n");
>> -		goto free_vqs;
>> +		goto free_bypass;
>> 	}
>>
>> 	virtio_device_ready(vdev);
>> @@ -2879,6 +3477,8 @@ static int virtnet_probe(struct virtio_device *vdev)
>> 	vi->vdev->config->reset(vdev);
>>
>> 	unregister_netdev(dev);
>> +free_bypass:
>> +	virtnet_bypass_destroy(vi);
>> free_vqs:
>> 	cancel_delayed_work_sync(&vi->refill);
>> 	free_receive_page_frags(vi);
>> @@ -2913,6 +3513,8 @@ static void virtnet_remove(struct virtio_device *vdev)
>>
>> 	unregister_netdev(vi->dev);
>>
>> +	virtnet_bypass_destroy(vi);
>> +
>> 	remove_vq_common(vi);
>>
>> 	free_netdev(vi->dev);
>> @@ -2996,6 +3598,11 @@ static __init int virtio_net_driver_init(void)
>> {
>> 	int ret;
>>
>> +	virtnet_bypass = bypass_register_driver(&virtnet_bypass_ops,
>> +						&virtnet_bypass_netdev_ops);
>> +	if (!virtnet_bypass)
>> +		return -ENOMEM;
> If CONFIG_NET_BYPASS is undefined, you will always return -ENOMEM here.

Will fix.


>
>
>> +
>> 	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "virtio/net:online",
>> 				      virtnet_cpu_online,
>> 				      virtnet_cpu_down_prep);
>> @@ -3010,12 +3617,14 @@ static __init int virtio_net_driver_init(void)
>>          ret = register_virtio_driver(&virtio_net_driver);
>> 	if (ret)
>> 		goto err_virtio;
>> +
>> 	return 0;
>> err_virtio:
>> 	cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
>> err_dead:
>> 	cpuhp_remove_multi_state(virtionet_online);
>> out:
>> +	bypass_unregister_driver(virtnet_bypass);
>> 	return ret;
>> }
>> module_init(virtio_net_driver_init);
>> @@ -3025,6 +3634,7 @@ static __exit void virtio_net_driver_exit(void)
>> 	unregister_virtio_driver(&virtio_net_driver);
>> 	cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
>> 	cpuhp_remove_multi_state(virtionet_online);
>> +	bypass_unregister_driver(virtnet_bypass);
>> }
>> module_exit(virtio_net_driver_exit);
>>
>> -- 
>> 2.14.3
>>

Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:

[...]

>> > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> > +				     struct net_device *child_netdev)
>> > +{
>> > +	struct virtnet_bypass_info *vbi;
>> > +	bool backup;
>> > +
>> > +	vbi = netdev_priv(bypass_netdev);
>> > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> > +			rtnl_dereference(vbi->active_netdev)) {
>> > +		netdev_info(bypass_netdev,
>> > +			    "%s attempting to join bypass dev when %s already present\n",
>> > +			    child_netdev->name, backup ? "backup" : "active");
>> Bypass module should check if there is already some other netdev
>> enslaved and refuse right there.
>
>This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>as its bypass_netdev is same as the backup_netdev.
>Will add a flag while registering with the bypass module to indicate if the driver is doing
>a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>for 3 netdev scenario.

Just let me undestand it clearly. What I expect the difference would be
between 2netdev and3 netdev model is this:
2netdev:
  bypass_master
     /
    /
VF_slave

3netdev:
  bypass_master
     /     \
    /       \
VF_slave   backup_slave

Is that correct? If not, how does it look like?

Thanks!

On 4/9/2018 1:07 AM, Jiri Pirko wrote:
> Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>> On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>>> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
> [...]
>
>>>> +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>>>> +				     struct net_device *child_netdev)
>>>> +{
>>>> +	struct virtnet_bypass_info *vbi;
>>>> +	bool backup;
>>>> +
>>>> +	vbi = netdev_priv(bypass_netdev);
>>>> +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>>>> +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>>>> +			rtnl_dereference(vbi->active_netdev)) {
>>>> +		netdev_info(bypass_netdev,
>>>> +			    "%s attempting to join bypass dev when %s already present\n",
>>>> +			    child_netdev->name, backup ? "backup" : "active");
>>> Bypass module should check if there is already some other netdev
>>> enslaved and refuse right there.
>> This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>> as its bypass_netdev is same as the backup_netdev.
>> Will add a flag while registering with the bypass module to indicate if the driver is doing
>> a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>> for 3 netdev scenario.
> Just let me undestand it clearly. What I expect the difference would be
> between 2netdev and3 netdev model is this:
> 2netdev:
>    bypass_master
>       /
>      /
> VF_slave
>
> 3netdev:
>    bypass_master
>       /     \
>      /       \
> VF_slave   backup_slave
>
> Is that correct? If not, how does it look like?
>
>
Looks correct.
VF_slave and backup_slave are the original netdevs and are present in both the models.
In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
marked as the 2 slaves of this new netdev.

In the 2 netdev model, backup_slave acts as bypass_master and the bypass module doesn't
have access to netdev_priv of the backup_slave.

Once i moved all the ndo_ops of the master netdev to bypass module, i realized that we can
move the create/destroy of the upper netdev also to bypass.c.
That way the changes to virtio_net become very minimal.

With these updates, bypass module now supports both the models by exporting 2 sets of
functions.
3 netdev:
    int bypass_master_create(struct net_device *backup_netdev,
                             struct bypass_master **pbypass_master);
    void bypass_master_destroy(struct bypass_master *bypass_master);


2 netdev:
    int bypass_master_register(struct net_device *backup_netdev, struct bypass_ops *ops,
                               struct bypass_master **pbypass_master);
    void bypass_master_unregister(struct bypass_master *bypass_master);

Will send the next revision in a day or two.

Thanks
Sridhar

Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>> Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>> > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>> [...]
>> 
>> > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> > > > +				     struct net_device *child_netdev)
>> > > > +{
>> > > > +	struct virtnet_bypass_info *vbi;
>> > > > +	bool backup;
>> > > > +
>> > > > +	vbi = netdev_priv(bypass_netdev);
>> > > > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> > > > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> > > > +			rtnl_dereference(vbi->active_netdev)) {
>> > > > +		netdev_info(bypass_netdev,
>> > > > +			    "%s attempting to join bypass dev when %s already present\n",
>> > > > +			    child_netdev->name, backup ? "backup" : "active");
>> > > Bypass module should check if there is already some other netdev
>> > > enslaved and refuse right there.
>> > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>> > as its bypass_netdev is same as the backup_netdev.
>> > Will add a flag while registering with the bypass module to indicate if the driver is doing
>> > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>> > for 3 netdev scenario.
>> Just let me undestand it clearly. What I expect the difference would be
>> between 2netdev and3 netdev model is this:
>> 2netdev:
>>    bypass_master
>>       /
>>      /
>> VF_slave
>> 
>> 3netdev:
>>    bypass_master
>>       /     \
>>      /       \
>> VF_slave   backup_slave
>> 
>> Is that correct? If not, how does it look like?
>> 
>> 
>Looks correct.
>VF_slave and backup_slave are the original netdevs and are present in both the models.
>In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>marked as the 2 slaves of this new netdev.

You say it looks correct and in another sentence you provide completely
different description. Could you please look again?

[...]

On 4/10/2018 3:55 AM, Jiri Pirko wrote:
> Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>> On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>>> Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>>>> On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>>>>> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>>> [...]
>>>
>>>>>> +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>>>>>> +				     struct net_device *child_netdev)
>>>>>> +{
>>>>>> +	struct virtnet_bypass_info *vbi;
>>>>>> +	bool backup;
>>>>>> +
>>>>>> +	vbi = netdev_priv(bypass_netdev);
>>>>>> +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>>>>>> +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>>>>>> +			rtnl_dereference(vbi->active_netdev)) {
>>>>>> +		netdev_info(bypass_netdev,
>>>>>> +			    "%s attempting to join bypass dev when %s already present\n",
>>>>>> +			    child_netdev->name, backup ? "backup" : "active");
>>>>> Bypass module should check if there is already some other netdev
>>>>> enslaved and refuse right there.
>>>> This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>>>> as its bypass_netdev is same as the backup_netdev.
>>>> Will add a flag while registering with the bypass module to indicate if the driver is doing
>>>> a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>>>> for 3 netdev scenario.
>>> Just let me undestand it clearly. What I expect the difference would be
>>> between 2netdev and3 netdev model is this:
>>> 2netdev:
>>>     bypass_master
>>>        /
>>>       /
>>> VF_slave
>>>
>>> 3netdev:
>>>     bypass_master
>>>        /     \
>>>       /       \
>>> VF_slave   backup_slave
>>>
>>> Is that correct? If not, how does it look like?
>>>
>>>
>> Looks correct.
>> VF_slave and backup_slave are the original netdevs and are present in both the models.
>> In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>> marked as the 2 slaves of this new netdev.
> You say it looks correct and in another sentence you provide completely
> different description. Could you please look again?
>
To be exact, 2 netdev model with netvsc looks like this.

     netvsc_netdev
       /
      /
  VF_slave

With virtio_net, 3 netdev model

   bypass_netdev
       /     \
      /       \
VF_slave   virtio_net netdev

Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>> Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>> > On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>> > > Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>> > > > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> > > > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>> > > [...]
>> > > 
>> > > > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> > > > > > +				     struct net_device *child_netdev)
>> > > > > > +{
>> > > > > > +	struct virtnet_bypass_info *vbi;
>> > > > > > +	bool backup;
>> > > > > > +
>> > > > > > +	vbi = netdev_priv(bypass_netdev);
>> > > > > > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> > > > > > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> > > > > > +			rtnl_dereference(vbi->active_netdev)) {
>> > > > > > +		netdev_info(bypass_netdev,
>> > > > > > +			    "%s attempting to join bypass dev when %s already present\n",
>> > > > > > +			    child_netdev->name, backup ? "backup" : "active");
>> > > > > Bypass module should check if there is already some other netdev
>> > > > > enslaved and refuse right there.
>> > > > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>> > > > as its bypass_netdev is same as the backup_netdev.
>> > > > Will add a flag while registering with the bypass module to indicate if the driver is doing
>> > > > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>> > > > for 3 netdev scenario.
>> > > Just let me undestand it clearly. What I expect the difference would be
>> > > between 2netdev and3 netdev model is this:
>> > > 2netdev:
>> > >     bypass_master
>> > >        /
>> > >       /
>> > > VF_slave
>> > > 
>> > > 3netdev:
>> > >     bypass_master
>> > >        /     \
>> > >       /       \
>> > > VF_slave   backup_slave
>> > > 
>> > > Is that correct? If not, how does it look like?
>> > > 
>> > > 
>> > Looks correct.
>> > VF_slave and backup_slave are the original netdevs and are present in both the models.
>> > In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>> > marked as the 2 slaves of this new netdev.
>> You say it looks correct and in another sentence you provide completely
>> different description. Could you please look again?
>> 
>To be exact, 2 netdev model with netvsc looks like this.
>
>    netvsc_netdev
>      /
>     /
> VF_slave
>
>With virtio_net, 3 netdev model
>
>  bypass_netdev
>      /     \
>     /       \
>VF_slave   virtio_net netdev

Could you also mark the original netdev which is there now? is it
bypass_netdev or virtio_net_netdev ?

On 4/10/2018 8:22 AM, Jiri Pirko wrote:
> Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>> On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>>> Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>>>> On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>>>>> Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>>>>>> On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>>>>>>> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>>>>> [...]
>>>>>
>>>>>>>> +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>>>>>>>> +				     struct net_device *child_netdev)
>>>>>>>> +{
>>>>>>>> +	struct virtnet_bypass_info *vbi;
>>>>>>>> +	bool backup;
>>>>>>>> +
>>>>>>>> +	vbi = netdev_priv(bypass_netdev);
>>>>>>>> +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>>>>>>>> +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>>>>>>>> +			rtnl_dereference(vbi->active_netdev)) {
>>>>>>>> +		netdev_info(bypass_netdev,
>>>>>>>> +			    "%s attempting to join bypass dev when %s already present\n",
>>>>>>>> +			    child_netdev->name, backup ? "backup" : "active");
>>>>>>> Bypass module should check if there is already some other netdev
>>>>>>> enslaved and refuse right there.
>>>>>> This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>>>>>> as its bypass_netdev is same as the backup_netdev.
>>>>>> Will add a flag while registering with the bypass module to indicate if the driver is doing
>>>>>> a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>>>>>> for 3 netdev scenario.
>>>>> Just let me undestand it clearly. What I expect the difference would be
>>>>> between 2netdev and3 netdev model is this:
>>>>> 2netdev:
>>>>>      bypass_master
>>>>>         /
>>>>>        /
>>>>> VF_slave
>>>>>
>>>>> 3netdev:
>>>>>      bypass_master
>>>>>         /     \
>>>>>        /       \
>>>>> VF_slave   backup_slave
>>>>>
>>>>> Is that correct? If not, how does it look like?
>>>>>
>>>>>
>>>> Looks correct.
>>>> VF_slave and backup_slave are the original netdevs and are present in both the models.
>>>> In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>>>> marked as the 2 slaves of this new netdev.
>>> You say it looks correct and in another sentence you provide completely
>>> different description. Could you please look again?
>>>
>> To be exact, 2 netdev model with netvsc looks like this.
>>
>>     netvsc_netdev
>>       /
>>      /
>> VF_slave
>>
>> With virtio_net, 3 netdev model
>>
>>   bypass_netdev
>>       /     \
>>      /       \
>> VF_slave   virtio_net netdev
> Could you also mark the original netdev which is there now? is it
> bypass_netdev or virtio_net_netdev ?

  bypass_netdev
      /     \
     /       \
VF_slave   virtio_net netdev (original)

Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
>On 4/10/2018 8:22 AM, Jiri Pirko wrote:
>> Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>> > On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>> > > Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>> > > > > Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> > > > > > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > [...]
>> > > > > 
>> > > > > > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> > > > > > > > +				     struct net_device *child_netdev)
>> > > > > > > > +{
>> > > > > > > > +	struct virtnet_bypass_info *vbi;
>> > > > > > > > +	bool backup;
>> > > > > > > > +
>> > > > > > > > +	vbi = netdev_priv(bypass_netdev);
>> > > > > > > > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> > > > > > > > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> > > > > > > > +			rtnl_dereference(vbi->active_netdev)) {
>> > > > > > > > +		netdev_info(bypass_netdev,
>> > > > > > > > +			    "%s attempting to join bypass dev when %s already present\n",
>> > > > > > > > +			    child_netdev->name, backup ? "backup" : "active");
>> > > > > > > Bypass module should check if there is already some other netdev
>> > > > > > > enslaved and refuse right there.
>> > > > > > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>> > > > > > as its bypass_netdev is same as the backup_netdev.
>> > > > > > Will add a flag while registering with the bypass module to indicate if the driver is doing
>> > > > > > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>> > > > > > for 3 netdev scenario.
>> > > > > Just let me undestand it clearly. What I expect the difference would be
>> > > > > between 2netdev and3 netdev model is this:
>> > > > > 2netdev:
>> > > > >      bypass_master
>> > > > >         /
>> > > > >        /
>> > > > > VF_slave
>> > > > > 
>> > > > > 3netdev:
>> > > > >      bypass_master
>> > > > >         /     \
>> > > > >        /       \
>> > > > > VF_slave   backup_slave
>> > > > > 
>> > > > > Is that correct? If not, how does it look like?
>> > > > > 
>> > > > > 
>> > > > Looks correct.
>> > > > VF_slave and backup_slave are the original netdevs and are present in both the models.
>> > > > In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>> > > > marked as the 2 slaves of this new netdev.
>> > > You say it looks correct and in another sentence you provide completely
>> > > different description. Could you please look again?
>> > > 
>> > To be exact, 2 netdev model with netvsc looks like this.
>> > 
>> >     netvsc_netdev
>> >       /
>> >      /
>> > VF_slave
>> > 
>> > With virtio_net, 3 netdev model
>> > 
>> >   bypass_netdev
>> >       /     \
>> >      /       \
>> > VF_slave   virtio_net netdev
>> Could you also mark the original netdev which is there now? is it
>> bypass_netdev or virtio_net_netdev ?
>
> bypass_netdev
>     /     \
>    /       \
>VF_slave   virtio_net netdev (original)

That does not make sense.
1) You diverge from the behaviour of the netvsc, where the original
   netdev is a master of the VF
2) If the original netdev is a slave, you cannot have any IP address
   configured on it (well you could, but the rx_handler would eat every
   incoming packet). So you will break the user bacause he would have to
   move the configuration to the new master device.
This only makes sense that the original netdev becomes the master for both
netvsc and virtio_net.

On Tue, Apr 10, 2018 at 8:43 AM, Jiri Pirko <jiri@resnulli.us> wrote:
> Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
>>On 4/10/2018 8:22 AM, Jiri Pirko wrote:
>>> Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>>> > On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>>> > > Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>>> > > > On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>>> > > > > Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>>> > > > > > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>>> > > > > > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>>> > > > > [...]
>>> > > > >
>>> > > > > > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>>> > > > > > > > +                                   struct net_device *child_netdev)
>>> > > > > > > > +{
>>> > > > > > > > +      struct virtnet_bypass_info *vbi;
>>> > > > > > > > +      bool backup;
>>> > > > > > > > +
>>> > > > > > > > +      vbi = netdev_priv(bypass_netdev);
>>> > > > > > > > +      backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>>> > > > > > > > +      if (backup ? rtnl_dereference(vbi->backup_netdev) :
>>> > > > > > > > +                      rtnl_dereference(vbi->active_netdev)) {
>>> > > > > > > > +              netdev_info(bypass_netdev,
>>> > > > > > > > +                          "%s attempting to join bypass dev when %s already present\n",
>>> > > > > > > > +                          child_netdev->name, backup ? "backup" : "active");
>>> > > > > > > Bypass module should check if there is already some other netdev
>>> > > > > > > enslaved and refuse right there.
>>> > > > > > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>>> > > > > > as its bypass_netdev is same as the backup_netdev.
>>> > > > > > Will add a flag while registering with the bypass module to indicate if the driver is doing
>>> > > > > > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>>> > > > > > for 3 netdev scenario.
>>> > > > > Just let me undestand it clearly. What I expect the difference would be
>>> > > > > between 2netdev and3 netdev model is this:
>>> > > > > 2netdev:
>>> > > > >      bypass_master
>>> > > > >         /
>>> > > > >        /
>>> > > > > VF_slave
>>> > > > >
>>> > > > > 3netdev:
>>> > > > >      bypass_master
>>> > > > >         /     \
>>> > > > >        /       \
>>> > > > > VF_slave   backup_slave
>>> > > > >
>>> > > > > Is that correct? If not, how does it look like?
>>> > > > >
>>> > > > >
>>> > > > Looks correct.
>>> > > > VF_slave and backup_slave are the original netdevs and are present in both the models.
>>> > > > In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>>> > > > marked as the 2 slaves of this new netdev.
>>> > > You say it looks correct and in another sentence you provide completely
>>> > > different description. Could you please look again?
>>> > >
>>> > To be exact, 2 netdev model with netvsc looks like this.
>>> >
>>> >     netvsc_netdev
>>> >       /
>>> >      /
>>> > VF_slave
>>> >
>>> > With virtio_net, 3 netdev model
>>> >
>>> >   bypass_netdev
>>> >       /     \
>>> >      /       \
>>> > VF_slave   virtio_net netdev
>>> Could you also mark the original netdev which is there now? is it
>>> bypass_netdev or virtio_net_netdev ?
>>
>> bypass_netdev
>>     /     \
>>    /       \
>>VF_slave   virtio_net netdev (original)
>
> That does not make sense.
> 1) You diverge from the behaviour of the netvsc, where the original
>    netdev is a master of the VF
> 2) If the original netdev is a slave, you cannot have any IP address
>    configured on it (well you could, but the rx_handler would eat every
>    incoming packet). So you will break the user bacause he would have to
>    move the configuration to the new master device.

That's exactly the point why I need to hide the lower netdev slaves
and trying the align the naming of the bypass with where IP was
configured on the original netdev. The current 3-netdev model is not
"transparent" by any means.

-Siwei

> This only makes sense that the original netdev becomes the master for both
> netvsc and virtio_net.

On 4/10/2018 8:43 AM, Jiri Pirko wrote:
> Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
>> On 4/10/2018 8:22 AM, Jiri Pirko wrote:
>>> Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>>>> On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>>>>> Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>>>>>> On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>>>>>>> Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>>>>>>>> On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>>>>>>>>> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>>>>>>> [...]
>>>>>>>
>>>>>>>>>> +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>>>>>>>>>> +				     struct net_device *child_netdev)
>>>>>>>>>> +{
>>>>>>>>>> +	struct virtnet_bypass_info *vbi;
>>>>>>>>>> +	bool backup;
>>>>>>>>>> +
>>>>>>>>>> +	vbi = netdev_priv(bypass_netdev);
>>>>>>>>>> +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>>>>>>>>>> +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>>>>>>>>>> +			rtnl_dereference(vbi->active_netdev)) {
>>>>>>>>>> +		netdev_info(bypass_netdev,
>>>>>>>>>> +			    "%s attempting to join bypass dev when %s already present\n",
>>>>>>>>>> +			    child_netdev->name, backup ? "backup" : "active");
>>>>>>>>> Bypass module should check if there is already some other netdev
>>>>>>>>> enslaved and refuse right there.
>>>>>>>> This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>>>>>>>> as its bypass_netdev is same as the backup_netdev.
>>>>>>>> Will add a flag while registering with the bypass module to indicate if the driver is doing
>>>>>>>> a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>>>>>>>> for 3 netdev scenario.
>>>>>>> Just let me undestand it clearly. What I expect the difference would be
>>>>>>> between 2netdev and3 netdev model is this:
>>>>>>> 2netdev:
>>>>>>>       bypass_master
>>>>>>>          /
>>>>>>>         /
>>>>>>> VF_slave
>>>>>>>
>>>>>>> 3netdev:
>>>>>>>       bypass_master
>>>>>>>          /     \
>>>>>>>         /       \
>>>>>>> VF_slave   backup_slave
>>>>>>>
>>>>>>> Is that correct? If not, how does it look like?
>>>>>>>
>>>>>>>
>>>>>> Looks correct.
>>>>>> VF_slave and backup_slave are the original netdevs and are present in both the models.
>>>>>> In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>>>>>> marked as the 2 slaves of this new netdev.
>>>>> You say it looks correct and in another sentence you provide completely
>>>>> different description. Could you please look again?
>>>>>
>>>> To be exact, 2 netdev model with netvsc looks like this.
>>>>
>>>>      netvsc_netdev
>>>>        /
>>>>       /
>>>> VF_slave
>>>>
>>>> With virtio_net, 3 netdev model
>>>>
>>>>    bypass_netdev
>>>>        /     \
>>>>       /       \
>>>> VF_slave   virtio_net netdev
>>> Could you also mark the original netdev which is there now? is it
>>> bypass_netdev or virtio_net_netdev ?
>> bypass_netdev
>>      /     \
>>     /       \
>> VF_slave   virtio_net netdev (original)
> That does not make sense.
> 1) You diverge from the behaviour of the netvsc, where the original
>     netdev is a master of the VF
> 2) If the original netdev is a slave, you cannot have any IP address
>     configured on it (well you could, but the rx_handler would eat every
>     incoming packet). So you will break the user bacause he would have to
>     move the configuration to the new master device.
> This only makes sense that the original netdev becomes the master for both
> netvsc and virtio_net.
Forgot to mention that bypass_netdev takes over the name of the original 
netdev and
virtio_net netdev will get the backup name.
So the userspace network configuration doesn't need to change.

Tue, Apr 10, 2018 at 05:59:02PM CEST, sridhar.samudrala@intel.com wrote:
>On 4/10/2018 8:43 AM, Jiri Pirko wrote:
>> Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
>> > On 4/10/2018 8:22 AM, Jiri Pirko wrote:
>> > > Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>> > > > > Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>> > > > > > > Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > > > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> > > > > > > > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > > [...]
>> > > > > > > 
>> > > > > > > > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> > > > > > > > > > +				     struct net_device *child_netdev)
>> > > > > > > > > > +{
>> > > > > > > > > > +	struct virtnet_bypass_info *vbi;
>> > > > > > > > > > +	bool backup;
>> > > > > > > > > > +
>> > > > > > > > > > +	vbi = netdev_priv(bypass_netdev);
>> > > > > > > > > > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> > > > > > > > > > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> > > > > > > > > > +			rtnl_dereference(vbi->active_netdev)) {
>> > > > > > > > > > +		netdev_info(bypass_netdev,
>> > > > > > > > > > +			    "%s attempting to join bypass dev when %s already present\n",
>> > > > > > > > > > +			    child_netdev->name, backup ? "backup" : "active");
>> > > > > > > > > Bypass module should check if there is already some other netdev
>> > > > > > > > > enslaved and refuse right there.
>> > > > > > > > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>> > > > > > > > as its bypass_netdev is same as the backup_netdev.
>> > > > > > > > Will add a flag while registering with the bypass module to indicate if the driver is doing
>> > > > > > > > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>> > > > > > > > for 3 netdev scenario.
>> > > > > > > Just let me undestand it clearly. What I expect the difference would be
>> > > > > > > between 2netdev and3 netdev model is this:
>> > > > > > > 2netdev:
>> > > > > > >       bypass_master
>> > > > > > >          /
>> > > > > > >         /
>> > > > > > > VF_slave
>> > > > > > > 
>> > > > > > > 3netdev:
>> > > > > > >       bypass_master
>> > > > > > >          /     \
>> > > > > > >         /       \
>> > > > > > > VF_slave   backup_slave
>> > > > > > > 
>> > > > > > > Is that correct? If not, how does it look like?
>> > > > > > > 
>> > > > > > > 
>> > > > > > Looks correct.
>> > > > > > VF_slave and backup_slave are the original netdevs and are present in both the models.
>> > > > > > In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>> > > > > > marked as the 2 slaves of this new netdev.
>> > > > > You say it looks correct and in another sentence you provide completely
>> > > > > different description. Could you please look again?
>> > > > > 
>> > > > To be exact, 2 netdev model with netvsc looks like this.
>> > > > 
>> > > >      netvsc_netdev
>> > > >        /
>> > > >       /
>> > > > VF_slave
>> > > > 
>> > > > With virtio_net, 3 netdev model
>> > > > 
>> > > >    bypass_netdev
>> > > >        /     \
>> > > >       /       \
>> > > > VF_slave   virtio_net netdev
>> > > Could you also mark the original netdev which is there now? is it
>> > > bypass_netdev or virtio_net_netdev ?
>> > bypass_netdev
>> >      /     \
>> >     /       \
>> > VF_slave   virtio_net netdev (original)
>> That does not make sense.
>> 1) You diverge from the behaviour of the netvsc, where the original
>>     netdev is a master of the VF
>> 2) If the original netdev is a slave, you cannot have any IP address
>>     configured on it (well you could, but the rx_handler would eat every
>>     incoming packet). So you will break the user bacause he would have to
>>     move the configuration to the new master device.
>> This only makes sense that the original netdev becomes the master for both
>> netvsc and virtio_net.
>Forgot to mention that bypass_netdev takes over the name of the original
>netdev and
>virtio_net netdev will get the backup name.

What do you mean by "name"?


>So the userspace network configuration doesn't need to change.
>
>

On 4/10/2018 11:03 PM, Jiri Pirko wrote:
> Tue, Apr 10, 2018 at 05:59:02PM CEST, sridhar.samudrala@intel.com wrote:
>> On 4/10/2018 8:43 AM, Jiri Pirko wrote:
>>> Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
>>>> On 4/10/2018 8:22 AM, Jiri Pirko wrote:
>>>>> Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>>>>>> On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>>>>>>> Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>>>>>>>> On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>>>>>>>>> Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>>>>>>>>>> On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>>>>>>>>>>> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>>>>>>>>> [...]
>>>>>>>>>
>>>>>>>>>>>> +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>>>>>>>>>>>> +				     struct net_device *child_netdev)
>>>>>>>>>>>> +{
>>>>>>>>>>>> +	struct virtnet_bypass_info *vbi;
>>>>>>>>>>>> +	bool backup;
>>>>>>>>>>>> +
>>>>>>>>>>>> +	vbi = netdev_priv(bypass_netdev);
>>>>>>>>>>>> +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>>>>>>>>>>>> +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>>>>>>>>>>>> +			rtnl_dereference(vbi->active_netdev)) {
>>>>>>>>>>>> +		netdev_info(bypass_netdev,
>>>>>>>>>>>> +			    "%s attempting to join bypass dev when %s already present\n",
>>>>>>>>>>>> +			    child_netdev->name, backup ? "backup" : "active");
>>>>>>>>>>> Bypass module should check if there is already some other netdev
>>>>>>>>>>> enslaved and refuse right there.
>>>>>>>>>> This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>>>>>>>>>> as its bypass_netdev is same as the backup_netdev.
>>>>>>>>>> Will add a flag while registering with the bypass module to indicate if the driver is doing
>>>>>>>>>> a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>>>>>>>>>> for 3 netdev scenario.
>>>>>>>>> Just let me undestand it clearly. What I expect the difference would be
>>>>>>>>> between 2netdev and3 netdev model is this:
>>>>>>>>> 2netdev:
>>>>>>>>>        bypass_master
>>>>>>>>>           /
>>>>>>>>>          /
>>>>>>>>> VF_slave
>>>>>>>>>
>>>>>>>>> 3netdev:
>>>>>>>>>        bypass_master
>>>>>>>>>           /     \
>>>>>>>>>          /       \
>>>>>>>>> VF_slave   backup_slave
>>>>>>>>>
>>>>>>>>> Is that correct? If not, how does it look like?
>>>>>>>>>
>>>>>>>>>
>>>>>>>> Looks correct.
>>>>>>>> VF_slave and backup_slave are the original netdevs and are present in both the models.
>>>>>>>> In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>>>>>>>> marked as the 2 slaves of this new netdev.
>>>>>>> You say it looks correct and in another sentence you provide completely
>>>>>>> different description. Could you please look again?
>>>>>>>
>>>>>> To be exact, 2 netdev model with netvsc looks like this.
>>>>>>
>>>>>>       netvsc_netdev
>>>>>>         /
>>>>>>        /
>>>>>> VF_slave
>>>>>>
>>>>>> With virtio_net, 3 netdev model
>>>>>>
>>>>>>     bypass_netdev
>>>>>>         /     \
>>>>>>        /       \
>>>>>> VF_slave   virtio_net netdev
>>>>> Could you also mark the original netdev which is there now? is it
>>>>> bypass_netdev or virtio_net_netdev ?
>>>> bypass_netdev
>>>>       /     \
>>>>      /       \
>>>> VF_slave   virtio_net netdev (original)
>>> That does not make sense.
>>> 1) You diverge from the behaviour of the netvsc, where the original
>>>      netdev is a master of the VF
>>> 2) If the original netdev is a slave, you cannot have any IP address
>>>      configured on it (well you could, but the rx_handler would eat every
>>>      incoming packet). So you will break the user bacause he would have to
>>>      move the configuration to the new master device.
>>> This only makes sense that the original netdev becomes the master for both
>>> netvsc and virtio_net.
>> Forgot to mention that bypass_netdev takes over the name of the original
>> netdev and
>> virtio_net netdev will get the backup name.
> What do you mean by "name"?

bypass_netdev also is associated with the same pci device as the original virtio_net
netdev via SET_NETDEV_DEV().  Also, we added ndo_get_phys_port_name() to virtio_net
that will return _bkup when BACKUP feature is enabled.

So for ex: if virtio_net inteface was getting 'ens12' as the name assigned by udev
without BACKUP feature,  when BACKUP feature is enabled,  the  bypass_netdev will be
named 'ens12' and the original virtio_net will get named as ens12n_bkup.


>
>> So the userspace network configuration doesn't need to change.
>>
>>

Wed, Apr 11, 2018 at 08:24:43AM CEST, sridhar.samudrala@intel.com wrote:
>On 4/10/2018 11:03 PM, Jiri Pirko wrote:
>> Tue, Apr 10, 2018 at 05:59:02PM CEST, sridhar.samudrala@intel.com wrote:
>> > On 4/10/2018 8:43 AM, Jiri Pirko wrote:
>> > > Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > On 4/10/2018 8:22 AM, Jiri Pirko wrote:
>> > > > > Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>> > > > > > > Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > > > On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>> > > > > > > > > Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > > > > > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> > > > > > > > > > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>> > > > > > > > > [...]
>> > > > > > > > > 
>> > > > > > > > > > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> > > > > > > > > > > > +				     struct net_device *child_netdev)
>> > > > > > > > > > > > +{
>> > > > > > > > > > > > +	struct virtnet_bypass_info *vbi;
>> > > > > > > > > > > > +	bool backup;
>> > > > > > > > > > > > +
>> > > > > > > > > > > > +	vbi = netdev_priv(bypass_netdev);
>> > > > > > > > > > > > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> > > > > > > > > > > > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> > > > > > > > > > > > +			rtnl_dereference(vbi->active_netdev)) {
>> > > > > > > > > > > > +		netdev_info(bypass_netdev,
>> > > > > > > > > > > > +			    "%s attempting to join bypass dev when %s already present\n",
>> > > > > > > > > > > > +			    child_netdev->name, backup ? "backup" : "active");
>> > > > > > > > > > > Bypass module should check if there is already some other netdev
>> > > > > > > > > > > enslaved and refuse right there.
>> > > > > > > > > > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>> > > > > > > > > > as its bypass_netdev is same as the backup_netdev.
>> > > > > > > > > > Will add a flag while registering with the bypass module to indicate if the driver is doing
>> > > > > > > > > > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>> > > > > > > > > > for 3 netdev scenario.
>> > > > > > > > > Just let me undestand it clearly. What I expect the difference would be
>> > > > > > > > > between 2netdev and3 netdev model is this:
>> > > > > > > > > 2netdev:
>> > > > > > > > >        bypass_master
>> > > > > > > > >           /
>> > > > > > > > >          /
>> > > > > > > > > VF_slave
>> > > > > > > > > 
>> > > > > > > > > 3netdev:
>> > > > > > > > >        bypass_master
>> > > > > > > > >           /     \
>> > > > > > > > >          /       \
>> > > > > > > > > VF_slave   backup_slave
>> > > > > > > > > 
>> > > > > > > > > Is that correct? If not, how does it look like?
>> > > > > > > > > 
>> > > > > > > > > 
>> > > > > > > > Looks correct.
>> > > > > > > > VF_slave and backup_slave are the original netdevs and are present in both the models.
>> > > > > > > > In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>> > > > > > > > marked as the 2 slaves of this new netdev.
>> > > > > > > You say it looks correct and in another sentence you provide completely
>> > > > > > > different description. Could you please look again?
>> > > > > > > 
>> > > > > > To be exact, 2 netdev model with netvsc looks like this.
>> > > > > > 
>> > > > > >       netvsc_netdev
>> > > > > >         /
>> > > > > >        /
>> > > > > > VF_slave
>> > > > > > 
>> > > > > > With virtio_net, 3 netdev model
>> > > > > > 
>> > > > > >     bypass_netdev
>> > > > > >         /     \
>> > > > > >        /       \
>> > > > > > VF_slave   virtio_net netdev
>> > > > > Could you also mark the original netdev which is there now? is it
>> > > > > bypass_netdev or virtio_net_netdev ?
>> > > > bypass_netdev
>> > > >       /     \
>> > > >      /       \
>> > > > VF_slave   virtio_net netdev (original)
>> > > That does not make sense.
>> > > 1) You diverge from the behaviour of the netvsc, where the original
>> > >      netdev is a master of the VF
>> > > 2) If the original netdev is a slave, you cannot have any IP address
>> > >      configured on it (well you could, but the rx_handler would eat every
>> > >      incoming packet). So you will break the user bacause he would have to
>> > >      move the configuration to the new master device.
>> > > This only makes sense that the original netdev becomes the master for both
>> > > netvsc and virtio_net.
>> > Forgot to mention that bypass_netdev takes over the name of the original
>> > netdev and
>> > virtio_net netdev will get the backup name.
>> What do you mean by "name"?
>
>bypass_netdev also is associated with the same pci device as the original virtio_net
>netdev via SET_NETDEV_DEV().  Also, we added ndo_get_phys_port_name() to virtio_net
>that will return _bkup when BACKUP feature is enabled.

Okay.

>
>So for ex: if virtio_net inteface was getting 'ens12' as the name assigned by udev
>without BACKUP feature,  when BACKUP feature is enabled,  the  bypass_netdev will be
>named 'ens12' and the original virtio_net will get named as ens12n_bkup.

Got it.

I don't like the bypass_master to look differently in netvsc and
virtio_net :/ The best would be to convert netvsc to 3 netdev model and
treat them the same. The more I think about it, the more the 2 netdev
model feels wrong.


>
>
>> 
>> > So the userspace network configuration doesn't need to change.
>> > 
>> > 
>

On Wed, Apr 11, 2018 at 10:03:32AM +0200, Jiri Pirko wrote:
> Wed, Apr 11, 2018 at 08:24:43AM CEST, sridhar.samudrala@intel.com wrote:
> >On 4/10/2018 11:03 PM, Jiri Pirko wrote:
> >> Tue, Apr 10, 2018 at 05:59:02PM CEST, sridhar.samudrala@intel.com wrote:
> >> > On 4/10/2018 8:43 AM, Jiri Pirko wrote:
> >> > > Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
> >> > > > On 4/10/2018 8:22 AM, Jiri Pirko wrote:
> >> > > > > Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
> >> > > > > > On 4/10/2018 3:55 AM, Jiri Pirko wrote:
> >> > > > > > > Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
> >> > > > > > > > On 4/9/2018 1:07 AM, Jiri Pirko wrote:
> >> > > > > > > > > Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
> >> > > > > > > > > > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
> >> > > > > > > > > > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
> >> > > > > > > > > [...]
> >> > > > > > > > > 
> >> > > > > > > > > > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
> >> > > > > > > > > > > > +				     struct net_device *child_netdev)
> >> > > > > > > > > > > > +{
> >> > > > > > > > > > > > +	struct virtnet_bypass_info *vbi;
> >> > > > > > > > > > > > +	bool backup;
> >> > > > > > > > > > > > +
> >> > > > > > > > > > > > +	vbi = netdev_priv(bypass_netdev);
> >> > > > > > > > > > > > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
> >> > > > > > > > > > > > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
> >> > > > > > > > > > > > +			rtnl_dereference(vbi->active_netdev)) {
> >> > > > > > > > > > > > +		netdev_info(bypass_netdev,
> >> > > > > > > > > > > > +			    "%s attempting to join bypass dev when %s already present\n",
> >> > > > > > > > > > > > +			    child_netdev->name, backup ? "backup" : "active");
> >> > > > > > > > > > > Bypass module should check if there is already some other netdev
> >> > > > > > > > > > > enslaved and refuse right there.
> >> > > > > > > > > > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
> >> > > > > > > > > > as its bypass_netdev is same as the backup_netdev.
> >> > > > > > > > > > Will add a flag while registering with the bypass module to indicate if the driver is doing
> >> > > > > > > > > > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
> >> > > > > > > > > > for 3 netdev scenario.
> >> > > > > > > > > Just let me undestand it clearly. What I expect the difference would be
> >> > > > > > > > > between 2netdev and3 netdev model is this:
> >> > > > > > > > > 2netdev:
> >> > > > > > > > >        bypass_master
> >> > > > > > > > >           /
> >> > > > > > > > >          /
> >> > > > > > > > > VF_slave
> >> > > > > > > > > 
> >> > > > > > > > > 3netdev:
> >> > > > > > > > >        bypass_master
> >> > > > > > > > >           /     \
> >> > > > > > > > >          /       \
> >> > > > > > > > > VF_slave   backup_slave
> >> > > > > > > > > 
> >> > > > > > > > > Is that correct? If not, how does it look like?
> >> > > > > > > > > 
> >> > > > > > > > > 
> >> > > > > > > > Looks correct.
> >> > > > > > > > VF_slave and backup_slave are the original netdevs and are present in both the models.
> >> > > > > > > > In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
> >> > > > > > > > marked as the 2 slaves of this new netdev.
> >> > > > > > > You say it looks correct and in another sentence you provide completely
> >> > > > > > > different description. Could you please look again?
> >> > > > > > > 
> >> > > > > > To be exact, 2 netdev model with netvsc looks like this.
> >> > > > > > 
> >> > > > > >       netvsc_netdev
> >> > > > > >         /
> >> > > > > >        /
> >> > > > > > VF_slave
> >> > > > > > 
> >> > > > > > With virtio_net, 3 netdev model
> >> > > > > > 
> >> > > > > >     bypass_netdev
> >> > > > > >         /     \
> >> > > > > >        /       \
> >> > > > > > VF_slave   virtio_net netdev
> >> > > > > Could you also mark the original netdev which is there now? is it
> >> > > > > bypass_netdev or virtio_net_netdev ?
> >> > > > bypass_netdev
> >> > > >       /     \
> >> > > >      /       \
> >> > > > VF_slave   virtio_net netdev (original)
> >> > > That does not make sense.
> >> > > 1) You diverge from the behaviour of the netvsc, where the original
> >> > >      netdev is a master of the VF
> >> > > 2) If the original netdev is a slave, you cannot have any IP address
> >> > >      configured on it (well you could, but the rx_handler would eat every
> >> > >      incoming packet). So you will break the user bacause he would have to
> >> > >      move the configuration to the new master device.
> >> > > This only makes sense that the original netdev becomes the master for both
> >> > > netvsc and virtio_net.
> >> > Forgot to mention that bypass_netdev takes over the name of the original
> >> > netdev and
> >> > virtio_net netdev will get the backup name.
> >> What do you mean by "name"?
> >
> >bypass_netdev also is associated with the same pci device as the original virtio_net
> >netdev via SET_NETDEV_DEV().  Also, we added ndo_get_phys_port_name() to virtio_net
> >that will return _bkup when BACKUP feature is enabled.
> 
> Okay.
> 
> >
> >So for ex: if virtio_net inteface was getting 'ens12' as the name assigned by udev
> >without BACKUP feature,  when BACKUP feature is enabled,  the  bypass_netdev will be
> >named 'ens12' and the original virtio_net will get named as ens12n_bkup.
> 
> Got it.
> 
> I don't like the bypass_master to look differently in netvsc and
> virtio_net :/ The best would be to convert netvsc to 3 netdev model and
> treat them the same. The more I think about it, the more the 2 netdev
> model feels wrong.

If you believe that, then this patchset is a step in the right
direction.

With something like this patchset applied, converting netvsc to a 3
device model will presumably be just a flag flip away. Afterwards
we'll be able to drop dead code handling the bypass_master flag.

> 
> >
> >
> >> 
> >> > So the userspace network configuration doesn't need to change.
> >> > 
> >> > 
> >

Wed, Apr 11, 2018 at 04:45:07PM CEST, mst@redhat.com wrote:
>On Wed, Apr 11, 2018 at 10:03:32AM +0200, Jiri Pirko wrote:
>> Wed, Apr 11, 2018 at 08:24:43AM CEST, sridhar.samudrala@intel.com wrote:
>> >On 4/10/2018 11:03 PM, Jiri Pirko wrote:
>> >> Tue, Apr 10, 2018 at 05:59:02PM CEST, sridhar.samudrala@intel.com wrote:
>> >> > On 4/10/2018 8:43 AM, Jiri Pirko wrote:
>> >> > > Tue, Apr 10, 2018 at 05:27:48PM CEST, sridhar.samudrala@intel.com wrote:
>> >> > > > On 4/10/2018 8:22 AM, Jiri Pirko wrote:
>> >> > > > > Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala@intel.com wrote:
>> >> > > > > > On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>> >> > > > > > > Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala@intel.com wrote:
>> >> > > > > > > > On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>> >> > > > > > > > > Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala@intel.com wrote:
>> >> > > > > > > > > > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> >> > > > > > > > > > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala@intel.com wrote:
>> >> > > > > > > > > [...]
>> >> > > > > > > > > 
>> >> > > > > > > > > > > > +static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
>> >> > > > > > > > > > > > +				     struct net_device *child_netdev)
>> >> > > > > > > > > > > > +{
>> >> > > > > > > > > > > > +	struct virtnet_bypass_info *vbi;
>> >> > > > > > > > > > > > +	bool backup;
>> >> > > > > > > > > > > > +
>> >> > > > > > > > > > > > +	vbi = netdev_priv(bypass_netdev);
>> >> > > > > > > > > > > > +	backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
>> >> > > > > > > > > > > > +	if (backup ? rtnl_dereference(vbi->backup_netdev) :
>> >> > > > > > > > > > > > +			rtnl_dereference(vbi->active_netdev)) {
>> >> > > > > > > > > > > > +		netdev_info(bypass_netdev,
>> >> > > > > > > > > > > > +			    "%s attempting to join bypass dev when %s already present\n",
>> >> > > > > > > > > > > > +			    child_netdev->name, backup ? "backup" : "active");
>> >> > > > > > > > > > > Bypass module should check if there is already some other netdev
>> >> > > > > > > > > > > enslaved and refuse right there.
>> >> > > > > > > > > > This will work for virtio-net with 3 netdev model, but this check has to be done by netvsc
>> >> > > > > > > > > > as its bypass_netdev is same as the backup_netdev.
>> >> > > > > > > > > > Will add a flag while registering with the bypass module to indicate if the driver is doing
>> >> > > > > > > > > > a 2 netdev or 3 netdev model and based on that flag this check can be done in bypass module
>> >> > > > > > > > > > for 3 netdev scenario.
>> >> > > > > > > > > Just let me undestand it clearly. What I expect the difference would be
>> >> > > > > > > > > between 2netdev and3 netdev model is this:
>> >> > > > > > > > > 2netdev:
>> >> > > > > > > > >        bypass_master
>> >> > > > > > > > >           /
>> >> > > > > > > > >          /
>> >> > > > > > > > > VF_slave
>> >> > > > > > > > > 
>> >> > > > > > > > > 3netdev:
>> >> > > > > > > > >        bypass_master
>> >> > > > > > > > >           /     \
>> >> > > > > > > > >          /       \
>> >> > > > > > > > > VF_slave   backup_slave
>> >> > > > > > > > > 
>> >> > > > > > > > > Is that correct? If not, how does it look like?
>> >> > > > > > > > > 
>> >> > > > > > > > > 
>> >> > > > > > > > Looks correct.
>> >> > > > > > > > VF_slave and backup_slave are the original netdevs and are present in both the models.
>> >> > > > > > > > In the 3 netdev model, bypass_master netdev is created and VF_slave and backup_slave are
>> >> > > > > > > > marked as the 2 slaves of this new netdev.
>> >> > > > > > > You say it looks correct and in another sentence you provide completely
>> >> > > > > > > different description. Could you please look again?
>> >> > > > > > > 
>> >> > > > > > To be exact, 2 netdev model with netvsc looks like this.
>> >> > > > > > 
>> >> > > > > >       netvsc_netdev
>> >> > > > > >         /
>> >> > > > > >        /
>> >> > > > > > VF_slave
>> >> > > > > > 
>> >> > > > > > With virtio_net, 3 netdev model
>> >> > > > > > 
>> >> > > > > >     bypass_netdev
>> >> > > > > >         /     \
>> >> > > > > >        /       \
>> >> > > > > > VF_slave   virtio_net netdev
>> >> > > > > Could you also mark the original netdev which is there now? is it
>> >> > > > > bypass_netdev or virtio_net_netdev ?
>> >> > > > bypass_netdev
>> >> > > >       /     \
>> >> > > >      /       \
>> >> > > > VF_slave   virtio_net netdev (original)
>> >> > > That does not make sense.
>> >> > > 1) You diverge from the behaviour of the netvsc, where the original
>> >> > >      netdev is a master of the VF
>> >> > > 2) If the original netdev is a slave, you cannot have any IP address
>> >> > >      configured on it (well you could, but the rx_handler would eat every
>> >> > >      incoming packet). So you will break the user bacause he would have to
>> >> > >      move the configuration to the new master device.
>> >> > > This only makes sense that the original netdev becomes the master for both
>> >> > > netvsc and virtio_net.
>> >> > Forgot to mention that bypass_netdev takes over the name of the original
>> >> > netdev and
>> >> > virtio_net netdev will get the backup name.
>> >> What do you mean by "name"?
>> >
>> >bypass_netdev also is associated with the same pci device as the original virtio_net
>> >netdev via SET_NETDEV_DEV().  Also, we added ndo_get_phys_port_name() to virtio_net
>> >that will return _bkup when BACKUP feature is enabled.
>> 
>> Okay.
>> 
>> >
>> >So for ex: if virtio_net inteface was getting 'ens12' as the name assigned by udev
>> >without BACKUP feature,  when BACKUP feature is enabled,  the  bypass_netdev will be
>> >named 'ens12' and the original virtio_net will get named as ens12n_bkup.
>> 
>> Got it.
>> 
>> I don't like the bypass_master to look differently in netvsc and
>> virtio_net :/ The best would be to convert netvsc to 3 netdev model and
>> treat them the same. The more I think about it, the more the 2 netdev
>> model feels wrong.
>
>If you believe that, then this patchset is a step in the right
>direction.
>
>With something like this patchset applied, converting netvsc to a 3
>device model will presumably be just a flag flip away. Afterwards

If done properly. Yes.

>we'll be able to drop dead code handling the bypass_master flag.
>
>> 
>> >
>> >
>> >> 
>> >> > So the userspace network configuration doesn't need to change.
>> >> > 
>> >> > 
>> >